1. Field of the Invention
The present invention relates to a method of the production of a nanoparticle dispersed composite material having nanoparticles within a substrate.
2. Description of the Related Art
In recent years, nanoparticle dispersed composite materials having nanoparticles formed on the surface of a substrate or within a base board have drawn great attention in the fields of material science as semiconductor quantum dot materials, metal nanoparticle dispersed composite materials and the like.
The semiconductor quantum dot materials have a structure in which semiconductor quantum dots comprising semiconductor single crystals are formed in a base board comprising other semiconductor single crystals. According to the materials having such a structure, manifestation of various physical properties or functions which can not be expected for conventional three dimensional semiconductors in a bulk state has been predicted.
According to the metal nanoparticle dispersed composite material, dispersed metal nanoparticles exhibit specific electronic properties, and photophysical properties, magnetism, conductive phenomenon of the metal nanoparticle interact mutually, therefore, manifestation of functions of the material having prominent added value has been expected utilizing such various properties. In the future, whether or not desired nanoparticle dispersed composite materials can be produced will be the key of development of the nanoparticle dispersed composite materials.
Methods of the production of a nanoparticle dispersed composite material that have been conventionally known are described below. FIG. 21 is a top perspective view schematically illustrating the first step of the most advanced method of the production of a semiconductor quantum dot material subjected to news release on 29, Jul. 2002 by Fujitsu Research Institute, and also reported in the 26th International congress on semiconductor physics (ICPS2002). First, as is shown in FIG. 21, a voltage is applied on a GaAs base board 51 by bringing a probe 52 of an atomic force microscope (AFM) into contact therewith. Such application of a voltage results in decomposition of the moisture included in the atmosphere into H+ and OH− by a local electric field formed by the probe 52, and the OH− leads to oxidation of a part of the base board 51 immediately below the probe 52 in a dot shape. Thus, an oxidized product 53 having the dot shape is formed on the base board 51. The diameter of the oxidized product 53 in the dot shape can be controlled by a time period of the oxidation, i.e., application time period of the voltage.
FIG. 22 is a cross sectional view schematically illustrating steps following FIG. 21 according to the method of the production described above. As is shown in FIG. 22 (a), the oxidized product 53 in the dot shape is removed by etching or the like (St 10), and as is shown in (b), recessions 54 are formed on the surface of the base board 51. Next, self organization of GaAs quantum dots 55 is allowed at only the recessions 54 by growth control that is referred to as Stranski-Krastanov mode (S-K mode) of a molecular beam epitaxy growth method (MBE method), as is shown in (c) (St 11). It is reported that production of semiconductor quantum dots with an arrangement of semiconductor quantum dots having a minimum diameter of 20 nm at intervals of several 10 nm is permitted, according to this method.
Appl. Phys. Lett., 75, (1999) 3488–3490, S. Kohmoto, et al., reported that production of semiconductor quantum dot materials with an arrangement of semiconductor quantum dots having a diameter of 30 nm at intervals of 45 nm is permitted by lithography on a GaAs base board in which a probe of a scanning tunneling microscope (STM) is used, and self organization growth of InAs using an MBE method.
Phys. Rev. B, 62, (2000) 16820–16825, S. Takeoka, et al., reported that semiconductor nanocrystals (Si, Ge, SiGe or the like) having a diameter of 2.5 to 9 nm are formed as a guest substance within a solid matrix thin membrane (SiO2, GeO2, Al2O3 or the like) by a simultaneous radio frequency sputtering method and a thermal treatment.
JP-A No. 11-45990 describes that a quantum device having only metal nanoparticles arranged on a base board is formed by arranging a protein internally including a metal nanoparticle on a base board followed by burning of the protein.
Furthermore, a technique in which formation of nanoparticles is allowed inside of a base board by ion implantation has been known. In such a technique, for example, masking is executed except for an opened region to which subjecting to ion implantation is intended on the surface of the base board, and an accelerated ion is implanted on the surface of the base board. For the formation of masking, a technique of photolithography is generally employed.
According to the method of the production in FIG. 21 and FIG. 22, the diameter of thus resulting semiconductor quantum dot is 20 nm at the minimum. According to the process for the production of dots, particle size, pitch and the like of the semiconductor quantum dot are dependent on precise control of the probe, therefore, it is difficult to obtain semiconductor quantum dots having a particle size of 10 nm or less, or to obtain semiconductor quantum dots arranged at pitches of 10 nm or less. In addition, possible manufacture was limited only to a 100 nm square, therefore, there existed a restriction of extremely low throughput. Further, because the dot shape according to the S-K mode growth is in a pyramid type or a dome type having a shorter height in comparison with the length of the bottom, a problem was raised of the aspect ratio being provided at most approximately fifth.
According to the method described in Appl. Phys. Lett., S. Kohmoto, et al., supra, there exists a limitation for the formation of a nanostructure, and it was impossible to obtain a semiconductor quantum dot material with semiconductor quantum dots having a diameter of, for example, 10 nm or less, which are arranged at intervals of, for example, 10 nm or less.
According to the method described in Phys. Rev., S. Takeoka, et al., supra, although the particle size of nanoparticles was reported as being 9.0 nm±1.8 nm, it was difficult to control and manufacture the particle size and arrangement essentially as the design of the device by the control of the concentration, temperature of the thermal treatment and time in such a method.
According to the method described in JP-A No. 11-459901, production of the nanoparticle dispersed composite material having nanoparticles within a base board was difficult.
Further, in the method according to the ion implantation, formation of the mask is generally conducted by photolithography, however, there exists limitation for the formation of the nanostructures. Thus, it was impossible to obtain semiconductor quantum dots with nanoparticles having a diameter of, for example, 10 nm or less, which are arranged at intervals of, for example, 10 nm or less.